Geno Toad Donkey Kong Jr Dark Pit Zoda Barker Bill Protoman Angry Nerd Rainbow Dash
Toad I imagine would be a joke character. Hold B to run away from other players, and waves his arms around in a comic fashion dealing low damage to anyone he happens to collide with. Down+B makes Toad cry.
DK Jr I think is a character who has a lot of potential he's never been allowed to live up too. Most people only know him from SNES Mario Kart, but I think that if Nintendo gave him another chance he could become more popular than the current Donkey Kong (who's actually DK Jr's son, so that's Jr Junior)
Dark Pit and Zoda would just look cool, imo. Barker Bill would be a "what the hell is he doing here" character. He'd also be a joke like Toad.
Protoman is like the cooler Megaman, and he has the proto-shield. He could also slide and charge his buster. And he has that sexy yellow scarf.
Angry Nerd would be hilarious, imo. He'd use NES accessories as weapons. Possibly OP.
And Rainbow Dash is Rainbow Dash. http://tinyurl.com/bhu6azv She'd be top tier and the strongest character debate would never be the same.
And I should have definitely included Dillon. Guys a freakin' armadillo! Maybe he could be on disc DLC?
Master of Gnomes, Keeper of Secrets Fluttershy's #1 Fan